The invention relates to aircraft of the type which employ a pressurized cabin and which fly at altitudes sufficiently high to require a supplemental oxygen system for use in the event of an emergency. More particularly, the invention relates to aircraft of the type designed to have the oxygen system mounted in a compartment in the upper back portion of the passenger seats. Typically, such a system is self-contained and includes oxygen masks, oxygen feed lines, an armed oxygen generating canister, and an electrically and mechanically activated compartment door release mechanism. During an emergency at altitude, the compartment door located on the rear surface of the passenger seat back will open, exposing the emergency system. Usually, two or three masks will be located in each compartment. Upon removal of any one mask by pulling it away from the compartment, a tether attached to the mask will activate the armed oxygen generating canister via a release pin attached to the inner end of the tether, causing oxygen to be generated by the reaction of certain chemicals and allowing it to flow to the masks. While the system is activated, the metal canister surface can reach a temperature of over 500.degree. F. due to the nature of the chemical reaction. The generation of oxygen, once started, cannot be stopped and will proceed for about 20 minutes. Although the oxygen canister is usually somewhat shielded by a perforated metal holder, there would be a possibility that one could burn his fingers if he touched the exposed canister. Also, if the emergency culminates in a hard landing, one's head might be thrown forward against the hot canister. In addition, the compartment containing the system is so deep and so high that it's forward wall would be quite hot in an area on the front of the seat back covered by only a relatively thin layer of foam. This could be uncomfortable or possibly burn a passenger pressing his head against the seat back. In addition, the large compartment size, dictated in good measure by the bulk of the canister, makes it necessary to have higher seat backs than would be desirable to permit comfortable viewing of a movie by many passengers. The vertical height requirement also makes it necessary to use folded tray tables or undesirably small tray tables in the backs of those seats containing the oxygen system. The great depth of the seat back necessitated to accommodate the oxygen system and provide a comfortable thickness of foam in front of it also encrouches on the living space of the passengers as compared to other seats which are spaced at the same distance or pitch but which do not include oxygen systems in their backs. For example, the seats cannot have as great a recline as they could if the seat backs could be made thinner. Also, the existing oxygen system compartment must be vented around the door to prevent excessive heat build-up if the canister were in some manner activated with the door closed or if the door was closed after activation. The vent space permits some cabin air to continually circulate through the compartment and makes it necessary for the interior of the compartment to be periodically cleaned and for smoke stains which might have gotten on the masks to be removed from the masks. Since most masks never get used, the time and expense spent in keeping the compartment clean would seem to be quite unproductive.